differential charge amplifier for processing charge signals from a rotation rate sensor, with a test signal being applied to the differential charge amplifier so that during normal operation the output of the amplifier corresponds to the test signal as well as to the charge signals.
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10. A differential charge amplifier for processing charge signals from a rotation rate sensor, with means for applying a test signal to the differential charge amplifier so that during normal operation the output of the amplifier corresponds to the test signal as well as to the charge signals.
8. A circuit for processing charge signals from pick-ups on a piezoelectric structure in a rotation rate sensor, comprising: a differential charge amplifier for providing an output signal corresponding to the charge signals from the pick-ups, and means for applying a test signal to the differential charge amplifier so that during normal operation the output signal corresponds to the test signal as well as to the charge signals.
3. In a differential charge amplifier for a rotation rate sensor having a piezoelectric structure with first and second pick-ups that provide charge signals corresponding to rotation of the structure: first and second charge amplifiers having first inputs to which the charge signals from respective ones of the pick-ups are applied and second inputs to which a reference is applied, means for applying a test signal to the second input of one of the charge amplifiers, and a difference amplifier responsive to output signals from the charge amplifiers.
1. A differential charge amplifier for a rotation rate sensor having a piezoelectric structure with first and second pick-ups that provide charge signals corresponding to rotation of the structure, comprising: a pair of input channels to which the charge signals are applied in a balanced differential manner, means for applying a test signal to the two input channels in an unbalanced manner so that the two channels produce different outputs in response to the test signal, and an output stage responsive to the difference between the outputs of the two input channels.
7. In a differential charge amplifier for a rotation rate sensor having a piezoelectric structure with first and second pick-ups that provide charge signals corresponding to rotation of the structure: a first charge amplifier having an inverting input to which the first pick-up is connected and a non-inverting input, means for applying a test signal to the non-inverting input of the first charge amplifier, a second charge amplifier having an inverting input to which the second pick-up is connected and a non-inverting input which is connected to a reference level, and a difference amplifier having an inverting input to which the output of the first charge amplifier is connected and a non-inverting input to which the output of the second charge amplifier is connected.
6. In a differential charge amplifier for a rotation rate sensor having a piezoelectric structure with first and second pick-ups that provide charge signals corresponding to rotation of the structure: a first charge amplifier having an inverting input to which the first pick-up is connected and a non-inverting input which is connected to a reference level, a second charge amplifier having an inverting input to which the second pick-up is connected and a non-inverting input, means for applying a test signal to the non-inverting input of the second charge amplifier, and a difference amplifier having an inverting input to which the output of the first charge amplifier is connected and a non-inverting input to which the output of the second charge amplifier is connected.
2. The differential charge amplifier of
4. The differential charge amplifier of
5. The differential charge amplifier of
9. The circuit of
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This invention pertains generally to rotation rate sensors and, more particularly, to a differential charge amplifier with a built-in test circuit for use in a rotation rate sensor.
Rate sensors with piezoelectric structures such as tuning forks rely on the Coriolis effect to sense rotation. The drive side of the tuning fork is driven in an oscillator circuit, with an automatic gain control (AGC) circuit keeping the current to the drive crystal constant. When the tuning fork is rotated, the pick-up tines develop an out-of-plane mode of vibration due to the Coriolis force. This vibration is detected piezoelectrically, and the resulting charge signal is directly proportional to the angular rate of rotation. That signal is converted from a charge signal to a voltage signal in a device known as a charge amplifier.
A commonly used charge amplifier circuit is shown in FIG. 1. This is a single-ended circuit in which the pick-up high electrode on the tuning fork is connected to the inverting input of the charge amplifier QA1, and the pick-up low electrode is connected to virtual ground Vg. A feedback resistor Rf and a feedback capacitor Cf are connected between the output and the inverting input of the amplifier. The resistive element provides a DC feedback path, and the capacitive element provides AC feedback. The capacitive element also provides the transfer function for the charge signal which is proportional to the angular rate at the drive fork frequency:
The non-inverting input of charge amplifier QA1 is also connected to virtual ground, and with a unipolar power supply, virtual ground is set to be one-half of the supply voltage in order to maximize the dynamic range of the amplifier. With a bipolar power supply, the pick-up low electrode and the non-inverting input of the charge amplifier are typically connected to a ground reference instead of the virtual ground.
By this process, the tuning fork and all of the gain stages in the forward rate channel are verified to be functional. If any of these elements should fail, the CBIT bias at the output will not be equal and opposite to the cancellation signal, and this shift in output is interpreted as an indication of the failure.
Being unbalanced circuits, the charge amplifiers of
The output of the differential amplifier can be either differential or single-ended. Although the charge amplifier of
The differential charge amplifier has several advantages over a single-ended circuit. It provides a 6 dB increase in signal-to-noise ratio (SNR) due to the gain of 2 in the differential circuit. The balanced structure provides increased common-mode rejection, which attenuates common-mode noise and further increases SNR. DC offset is also greatly attenuated because the circuit has a large common-mode rejection at DC.
The differential charge amplifier of
It is in general an object of the invention to provide a new and improved charge amplifier.
Another object of the invention is to provide a charge amplifier of the above character which overcomes the limitations and disadvantages of the prior art.
These and other objects are achieved in accordance with the invention by providing a differential charge amplifier for processing charge signals from a rotation rate sensor, and means for applying a test signal to the differential charge amplifier so that during normal operation the output of the amplifier corresponds to the test signal as well as to the charge signals.
As illustrated in
A test signal CBIT is applied to the inputs of the charge amplifiers in an unbalanced manner so as to produce different outputs from the two amplifiers during normal operating conditions. In the embodiment of
The outputs of charge amplifiers QA1, QA2 are connected to the inverting and non-inverting inputs of a difference amplifier 16 in the output stage 17 of the circuit. This amplifier can be either single-ended or differential, and it produces an output signal which corresponds to the difference in the outputs of the two charge amplifiers produced by the CBIT signal.
The embodiment of
In both embodiments, the shunt capacitance C0 of the piezoelectric structure essentially becomes a common component of parallel voltage gain paths which have common amplification factors. This generates the offset signal to be monitored. By applying the CBIT signal to the reference input, it is isolated from the balanced input circuit by the high input impedance of the charge amplifier to which it is applied.
Operation of the two embodiments is similar except that injecting the CBIT signal into the non-inverting input of charge amplifier QA1 generates a negative built-in test (BIT) rate signal, whereas injection into the non-inverting input of charge amplifier QA2 generates a positive BIT rate signal. If a pickup fork connection breaks, the output of difference amplifier 16 shifts positively for CBIT injection into charge amplifier QA1 and negatively for CBIT injection into charge amplifier QA2. In either case, the shift is toward the nominal zero rate output level, which in the embodiments illustrated is virtual ground.
As illustrated in
The equivalent CBIT circuit corresponding to
The other path for the CBIT signal is an inverting gain amplifier formed by the combination by charge amplifier QA1 and shunt capacitance C0. The input signal to this amplifier is the CBIT signal which is present at the inverting input of charge amplifier QA2, and the output signal from this amplifier, -(C0/Cd1)·VCBIT, is applied to the negative input of difference amplifier 16.
The normal, steady state output of the difference amplifier, whether single-ended or differential, is an a.c. bias signal with a value
where K is the gain of the amplifier and Cd=C1=C2. If the pick-up fork breaks, the shunt capacitor C0 will disconnect, causing a change in the output signal which will then have the value
Moreover, if any component fails in the forward rate channel path, a detectable shift in output shall occur as the CBIT signal and the cancellation signal generated further down the rate signal path will not null each other out any more. The magnitude of the signal shift for CBIT failure detection is
The invention has a number of important features and advantages. It provides a balanced differential circuit for charge amplification with CBIT injection which produces an offset for fault detection. In addition, a break in the pick-up fork connection produces an output signal that can be detected as a failure in the forward rate channel path.
It is apparent from the foregoing that a new and improved charge amplifier has been provided. While only certain presently preferred embodiments have been described in detail, as will be apparent to those familiar with the art, certain changes and modifications can be made without departing from the scope of the invention as defined by the following claims.
Patent | Priority | Assignee | Title |
10288426, | Mar 16 2015 | Seiko Epson Corporation | Circuit device, physical-quantity detecting apparatus, electronic apparatus, and moving object |
7783446, | May 07 2004 | KISTLER HOLDING AG | Measuring system comprising variably sensitive outputs |
9219430, | Dec 21 2010 | HIDRIA, RAZVOJ IN PROIZVODNJA AVTOMOBILSKIH IN INDUSTRIJSKIH SISTEMOV, D O O HIDRIA D O O | Sensor comprising a piezoelectric detector with compensation for ground faults |
Patent | Priority | Assignee | Title |
5220836, | Apr 27 1989 | AVL Gesellschaft fur Verbrennungskraftmaschinen und Messtechnick mbH., | Method and arrangement for piezoelectric measurement |
5388458, | Nov 24 1992 | CHARLES STARK DRAPER LABORATORY, INC , THE | Quartz resonant gyroscope or quartz resonant tuning fork gyroscope |
5426970, | Aug 02 1993 | BEI SENSORS & SYSTEMS COMPANY, INC , A CORP OF DELAWARE | Rotation rate sensor with built in test circuit |
5453604, | Jun 03 1993 | Sony Corporation | Binary circuit and image pick-up apparatus including such binary circuit |
5600063, | Aug 24 1994 | Mitsubishi Denki Kabushiki Kaisha | Oscillation gyro and an inspection apparatus therefor |
5654550, | Sep 28 1994 | Murata Manufacturing Co., Ltd. | Signal processor for pyroelectric infrared sensor |
WO107875, |
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